1. Field of the Invention
The present invention relates to a wireless communication system. More particularly, the present invention relates to an apparatus and a method for selecting a beam in a wireless communication system that uses a plurality of antenna beams.
2. Description of the Related Art
Wireless communication systems can increase a data transmission rate by using a beamforming technique. The beamforming technique refers to a series of techniques that can improve transmission/reception (TX/RX) performance by using high-gain antennas.
When the beamforming technique is used, a wireless communication system should reduce the width of an antenna beam in order to increase an antenna gain. In this case, the wireless communication system should use a plurality of narrow-width beams (hereinafter referred to as narrow beams) in order to transmit a signal in all directions.
A wireless communication system beamforms not only data but also a synchronization (sync) signal and a common control signal. The sync signal and the common control signal are used commonly by a plurality of Mobile Stations (MSs). Accordingly, when narrow beams are used to transmit a sync signal and a common control signal, a Base Station (BS) has an overhead of having to repeatedly transmit the same sync signal and the same common control signal through narrow beams in all directions.
In order to reduce a beamforming overhead by a sync signal and a common control signal, a wireless communication system uses wide beams to transmit the sync signal and the common control signal.
However, when a wireless communication system uses wide beams, an inter-signal interference increases due to multi-path fading.
Furthermore, when using an Orthogonal Frequency Division Multiplexing (OFDM) scheme, the wireless communication system sets a Cyclic Prefix (CP) to be large in order to reduce an OFDM inter-symbol interference. In this case, an overhead increases due to the CP in the wireless communication system.
When a transmitting terminal changes a narrow beam transmitting a signal, a signal interference occurs due to multi-path fading in the wireless communication system as in the case of using wide beams.
In order to increase a transmission rate, the wireless communication system may simultaneously communicate signals with a plurality of mobile stations by using a plurality of beams. In this case, in the wireless communication system, a signal interference may occur due to multi-path fading by signals communicated with other mobile stations.
Therefore, a need exists for an apparatus and a method for reducing a beamforming overhead in a wireless communication system using a beamforming technique.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.